Let's assume that the VOB files are already on the hard drive, so that
it's possible to operate on all of them in parallel. Transcode loves to have a lot
of processing power, so giving it many separate processors will make it very happy.

The reason to use a separate work directory here is that xvid4 creates a
file called "divx4.log" in the current working directory, so otherwise it
would become overwritten if multiple instances of this script were to run:

cd /work_dir/$COUNT

Set the resize parameter. Quite a confusing parameter indeed.

export RESIZE="-B 12,10,8"

Use a bitrate ranging from as low as 500 to as high as 2500, depending on
how large a screen you intend to playback the resulting xvid:

export BITRATE="-w 1500,250,100"

If you see thin horizontal lines on fast motion, you need to deinterlace:

export DEINTERLACE="-I 3"

If you want to keep the original AC3 soundtrack rather than encode it to mp3,
e.g. if you are using an external "receiver", use this:

export AC3PASSTHRU="-A -N 0x2000"

Invoke the first pass of transcode, this is to allow the xvid encoder to figure
out the best amount of compression to use, depending on the content of the source.
The use of the "-M 2" flag can help to keep the audio in sync with the video: